Buy option contract when underlying trades below specified price

The question title you entered was missing the details required to help folks understand the context of your request: "How to create conditional order on ThinkorSwim"

There are dozens of posts in the forum that explain how to create conditional orders and we have a video that explains everything. So that question title does not mean anything at all. The title of the question has been updated to explain the context of your request, which enables the rest of our viewers to search for an find this specific solution.

There is no stock ticker "XYZ". We need a specific example and not a theoretical one.

There is absolutely no code required for this. Everything is within reach of anyone that knows how to use a mouse or trackpad.

The following screenshot demonstrates each step required to setup a conditional order to buy one .AAPL200619C315 contract when the price of the underlying "AAPL" Mark price is less than or equal to 310.00.

Notice there is no time frame to select in this example because none is required. Price trading above or below a specific value requires no specific time frame.

In the comments section of the original answer I provided I discovered the request is specifically for a 3 min bar to completely close above the key level. So that means all four data points of the candle, (open, high, low and close).

We only need to use one data point for this, the low. So we build a signal that checks if the former candle has a low below the key level and the current candle has a low that is above the key level. (for the opposite side of this request we use the high of the candle, reverse the signs and change the value of the key level).

def pattern = low[1] < 310.0 and low > 310.0;

Now we can't use that directly, because we need to wait for that bar to close. So we add a second line that checks if that pattern was true on the previous bar. Here are both lines together:

def pattern = low[1] < 310.0 and low > 310.0;
plot trigger = pattern[1];

We could have done that all in one line but this makes it more clear exactly what the code is doing. So you create an order to buy the specific option contract your setup requires, then access the code editor for the conditional order and insert this code.

I have included a new screenshot below that shows all the elements required to put this together. Drawings indicate those fields that required user input to create and set the various elements.

For those that are looking at this screenshot and feel completely lost. No worries. I explain how to use this tool step-by-step using several examples in the following video:

https://www.hahn-tech.com/thinkorswim-autotrade-almost/

Note the title of the question requests a method to buy when the underlying trades below a specified price while in the body of the question the request is for both. So here I am showing how to trigger the order when the underlying closes above the key level. You can flip things around to perform the opposite side of this request.